// 通用类名
$num_list:1,2,3,4,5;

@each $num in $num_list {
  .ml-#{$num}{
    margin-left: $num * 4px;
  }
  .mr-#{$num}{
    margin-right: $num * 4px;
  }
  .mt-#{$num}{
    margin-top: $num * 4px;
  }
  .mb-#{$num}{
    margin-bottom: $num * 4px;
  }
  .pl-#{$num}{
    padding-left: $num * 4px;
  }
  .pr-#{$num}{
    padding-right: $num * 4px;
  }
  .pt-#{$num}{
    padding-top: $num * 4px;
  }
  .pb-#{$num}{
    padding-bottom: $num * 4px;
  }
}
